Pitch black planet

Sep. 25th, 2017 07:48 pm
[syndicated profile] badastronomy_feed

Posted by Phil Plait

Over a thousand light from Earth, there is a decidedly odd planet. It orbits the star WASP-12 — named so because it was the 12th star found to have a planet by the Wide Angle Search for Planets consortium. The star is somewhat more massive and hotter than our own Sun, and the planet is called WASP-12b, as is the convention.

This is no planet like we have in our own solar system. The closest analogue would be Jupiter; WASP-12b is about 40% more massive. But a funny thing was discovered immediately upon its discovery: It’s much larger than Jupiter, almost twice its diameter. That is very peculiar. When planets get to be around the mass of Jupiter, an odd quirk of physics called degeneracy kicks in, which changes how the material inside the planet behaves under pressure. When you add mass to such a planet, it actually gets smaller, not larger.

So, why is WASP-12b more massive than Jupiter, and larger? Because it’s hot. Really hot. It orbits its star a mere 3 million kilometers above its surface, far closer even than Mercury orbits or Sun! Its proximity means the planet is broiled by the star, and may have a temperature of 2300° Celsius (almost 4200° F) at its cloud tops. That heat puffs up the outer atmosphere, making the planet larger than you’d expect for its mass.

And now, astronomers have discovered something else that’s bizarre about the planet: It’s dark. Like really unusually so. Most planets reflect quite a bit of light that falls on them from their star; for example, Earth is about 40% reflective (in astronomer lingo this is what we’d call an albedo of 0.4). However, new observations of WASP-12b show it reflects a mere 6% of the light that hits it (an albedo of 0.06), roughly the same albedo as asphalt. And that’s an upper limit! It might even be darker.

This was discovered in a clever set of observations using the Space Telescope Imaging Spectrograph (STIS) — a camera on board the Hubble Space Telescope that can break light up into separate colors and analyze it. In a sense, it spreads the light out like a rainbow, but a rainbow with hundreds or thousands of colors. By examining the resulting spectrum, we can learn a lot about the object giving off that light.

WASP-12b lends itself well to this type of camera. That’s because, due to a favorable geometry, we see it orbiting its star edge-on from Earth. That means, once every orbit, it passes directly in front of its star, blocking a fraction of the light. But that also means that, half an orbit later, it passes directly behind its star. Most of the time during its orbit, we see the light from the planet and the star together, but, for that short time while it’s eclipsed, we see only the light from the star.

The star is bright enough that seeing the dip in light when the planet blocks it isn’t too hard. But the planet is faint — literally a billion or so times fainter — so seeing the light from the system drop when the planet is in eclipse is extremely difficult. However, STIS is quite an amazing machine, and is capable of making this observation*.

The observations were made right before, during, and after an eclipse. Right as the planet slips behind the star, the light should drop, and then it should come back up when the eclipse is over. And what they found was...nothing. As in, the amount of light they saw in every color was fairly steady, when it should have dropped a bit. The only explanation is that the planet is absorbing nearly all the star’s light that falls on it, reflecting almost none. It’s dark.

spectrum of WASP-12b

 

This plot shows how deep the eclipse was (vertical axis, measured in parts per million) versus color (horizontal; 300 nanometers is blue and 550 is yellow). The observations are very flat and nearly 0 within the uncertainty bars, meaning essentially no light was reflected by the planet. The grey line would be what’s expected for a planet with haze, and the blue line for one without clouds. The red line is for a planet simply glowing under its own heat. Credit:...

That’s interesting right away. A couple of previous observations made of the planet indicated that it might not have any clouds in it (not water clouds like on Earth — at those temperatures, water gets ripped apart into its individual hydrogen and oxygen atoms — but some other material that can condense in the upper atmosphere), or it might have an atmosphere of aluminum oxide haze. However, either of these two cases would show a change not only in brightness during the eclipse, but also a change in color (for example, clouds in the planet’s atmosphere would reflect more blue light, so the spectrum would show a bigger drop in blue light than red if the clouds were there). Yet neither of those two models fits the STIS spectra. Instead, it’s more likely WASP-12b has an atmosphere of hydrogen and helium. Those gasses absorb all the light coming from the star, which is why it’s so dark.

Another interesting thing: The planet orbits so close to its star that it should be tidally locked to it; that is, spin once for every time it orbits (this happens naturally over time when any object closely orbits another, like our own Moon). That means one side always faces the star, and the other faces away. When it’s about to be eclipsed, we only see the day side of the planet (it’s on the other side of the star from us, so we see it fully illuminated) where it’s very hot. But temperatures on the night side may be much lower, by as much as 1000°C. That means different chemistry can occur there, and there may yet be water vapor and other materials that can condense to form clouds. We just don’t see them in this observation because they’re on the other side of the planet.

What an odd place.

 

And there’s yet one more thing. The press release for this news says the planet is “pitch black”, which is fair enough. But by that they mean the planet is dark, non-reflective. This doesn’t refer to the actual color of the planet, just the brightness! My friend Kiki Sanford (who runs the wonderful This Week in Science podcast) asked me about this, and makes a good point: At 2300° C, the planet should actually glow under its own heat.

She’s right. Anything above a temperature of absolute zero emits light, and the warmer it is, the higher energy the light is. At WASP-12b’s temperature, it should peak in the infrared, just outside what our eyes can see. But that’s just where it would emit the most light; it still should emit some light in visible colors. It does, but not much. The STIS spectra are consistent with it being very slightly red, which is what I’d expect for such an object, but they’re not conclusive.

Still, that’s a funny thing to think about: It’s emitting its own light, faintly, but at the same time, it’s so absorbent it reflects almost none from the star. If it had a reflectivity like Earth it would look far brighter due to reflected starlight than from its own internal heat.

So, if you were floating next to it, would you see it? Almost certainly yes. Unless it reflects absolutely no light at all, it’s so close to the star that a lot of light is falling on it, so even if the albedo is, say, 0.01 (and it’s hard to see how anything could be that dark), it would still reflect enough light to see.

So, “pitch black” is an accurate term, but a little misleading. It’s not black, per se. It’s reddish, but it’s dark.

Hmmm. “Dark planet” is actually a rather more foreboding term, isn’t it? I like it better. It’s cooler (though not literally).

And it’s weird. The only other exoplanet we’ve been able to observe via reflected light is HD189733b (which, like WASP-12b, is a hot near-Jupiter-mass planet), but it’s far cooler and tends to reflect light better in the blue. This means its atmosphere must be very different than WASP-12b’s.

We’ve observed two planets like these in this way, and they’re very different. That’s exciting: It means that “hot Jupiters” are diverse, and that, in turn, means that every one we observe will tell us something important. Studying exoplanets in this way is a very new science; we’ve only just started here. I can’t wait to see what else we’ll discover!

* If I sound like I’m bragging, why, yes, I am: I was on the team that built STIS and I helped calibrate before and after launch. Despite that, it works very well.  

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Artwork depicting WASP-12b orbiting its star. NASA, ESA, and G. Bacon (STScI)

the hilarious world of depression

Sep. 25th, 2017 05:05 pm
[syndicated profile] wwdn_feed

Posted by Wil

I spoke with John Moe about my mental illness for his podcast, The Hilarious World of Depression:

Wil Wheaton was a child star in Stand By Me, a regular on Star Trek: The Next Generation as a teenager, and has been trying to figure out his role in show business for a long time since then. He was dealing with the pressures of fame and the fickle tastes of Hollywood, all while dealing with a chemical imbalance in his brain that made him prone to anxiety and depression. Wil’s better now thanks to medication, but despite his long IMDb page and regular work on The Big Bang Theory, his hit YouTube show, and a thriving and varied career, he sees himself primarily as a failed actor.

It’s a good show, as they say. Go give it a listen.

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How can disadvantaged students succeed in school? For sociologist Anindya Kundu, grit and stick-to-itiveness aren't enough; students also need to develop their agency, or their capacity to overcome obstacles and navigate the system. He shares hopeful stories of students who have defied expectations in the face of personal, social and institutional challenges.
[syndicated profile] badastronomy_feed

Posted by Phil Plait

If I ask you to close your eyes and picture an asteroid, you’ll probably think of a gray, battered, vaguely spherical object with lots of craters.

If I ask you now to picture a comet, you’ll probably think of a bright fuzzy thing with a long, diffuse tail.

However, nature cares not for your arbitrary distinction between cosmic objects! Sometimes, we find things that straddle the line between two different categories. And oh, my, does 300163 (2006 VW139) push every boundary we have for such things.

This object was discovered in 2006 by Spacewatch, a program dedicated to finding small objects in the solar system. It orbits the Sun between Mars and Jupiter, in what’s called the main asteroid belt. The orbit was determined to be fairly elliptical, which is unusual for an asteroid but not too shocking.

The orbit of the weird binary asteroid/comet 2006 VW139, also called 288P. Its position is shown for Nov. 6, 2016, when it was at perihelion, closest to the Sun. Credit: NASA/JPL

The orbit of the weird binary asteroid/comet 2006 VW139, also called 288P. Its position is shown for Nov. 6, 2016, when it was at perihelion, closest to the Sun. Credit: NASA/JPL

 

Then things got weird. In 2011, observations using Pan-STARRS revealed VW139 was surrounded by a halo of dust, and had trails of dust streaming out away from it. Sometimes asteroids get these haloes if they suffer a collision with another asteroid and material gets blown out. But observations over the course of a month showed no change in the halo’s brightness — you’d expect stuff blasted out by a collision to expand and fade over a few days. This meant the object was continuously producing dust, blowing it off the surface.

That makes it more like a comet: While asteroids are nearly all rock and/or metal, comets are rock and various ices (like frozen water, carbon dioxide, and carbon monoxide). So it was then reclassified as a main belt comet and given the second name of P/2006 VW139 (as well as, confusingly, 288P, which is how most press releases refer to it, but from here on out I’ll just call VW139).

But now the plot has thickened again. Observations using the Hubble Space Telescope in late 2016 (when the object was closest both to Earth and the Sun) revealed yet another surprise: VW139 is binary!

 

Instead of being a single object, it’s actually two large chunks orbiting each other. Even with Hubble, these were tough observations, and it’s hard to constrain the physical characteristics of the two chunks and their mutual orbit around each other. But it’s likely each chunk is on the order of a kilometer or so across. Models of their motion can’t pin down the orbital period, but the model solutions tend to fall into three different groups of 103, 135, and 175 days (meaning one of these is likely the correct period, but it’s not clear which one).

The orbit of the two chunks around each other is likely highly elliptical, meaning it’s not even close to being a circle. Ellipses are in part defined their semi-major axes, the distance from the center of the orbit to the most distant part. For VW139, this distance is likely to be between 70 and 140 kilometers, which is yet another oddity.

Why? Well, we’ve discovered lots of binary asteroids, but in most cases, the two components are very different sizes, and the orbits are much smaller compared to the size of the objects (that is, the two bodies orbit pretty tightly) and not nearly so elliptical. The mutual orbit of the chunks in VW139 is a hundred or so times the size of the chunks themselves, which is very wide.

Images of the comet P/2006 VW139 using Hubble show it to be a binary pair of objects.Credit: NASA, ESA, and J. Agarwal (Max Planck Institute for Solar System Research)

Images of the comet P/2006 VW139 using Hubble show it to be a binary pair of objects.Credit: NASA, ESA, and J. Agarwal (Max Planck Institute for Solar System Research)

 

So, what is this thing, and how did it form? Well, a big clue is that it seems to be most active when it’s closer to the Sun in its orbit. That is a strong indicator that it has water ice in it, and as it warms up that turns directly into a gas (this is called sublimation). Using physical models of how the dust reflects light, astronomers think that this first releases pieces of rock the size of gravel, but over time, finer-grained material lifts off as well. Eventually, as VW139 moves away from the Sun, the activity drops, and some of the dust settles back down, to be released the next time the comet warms up (it has an orbit about 2.6 years long).

Interestingly, surface ice on an object like this cannot exist for long at this distance from the Sun, certainly not for billions of years. So it’s likely that some relatively recent event — perhaps just a few thousand years ago — split a large object in two, forming the binary. It may have been a collision, but another possibility is that the single object got spun up by outside forces (sunlight can actually do this via a process called the YORP effect) and the centrifugal force broke it apart. Either way, freshly revealed ice would then sublimate and blow outward, and this can contribute to separating the two chunks into their current wide spacing.

I do so love stories like this. When I was a kid, asteroids were asteroids and comets were comets. Then x`we started seeing objects on that border between them, dead comets that look like asteroids and asteroids that blew off material like comets. It was hard to accept at first, but now we see that there is an even finer degree of resolution in this spectrum, likely with objects all along the line between the two ends. Nature was telling us not to be so rigid in our beliefs, engendering a wider view by scientists, a willingness to accept that not everything in life is either one thing or the other.

I find that transformative, and wonderful. It makes life so much more diverse and interesting!

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Images of the comet P/2006 VW139 using Hubble show it to be a binary pair of objects.Credit: NASA, ESA, and J. Agarwal (Max Planck Institute for Solar System Research)

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Sep. 25th, 2017 07:24 am
copperbadge: (radiofreemondaaay)
[personal profile] copperbadge
Good morning everyone, and welcome to Radio Free Monday!

Ways To Give:

Anon linked to a fundraiser for [tumblr.com profile] onomatopathetically, a disabled woman trapped in an abusive and dangerous home situation. She's raising funds to relocate to somewhere safe where she can get a job; you can read more and support the fundraiser here.

[personal profile] pinesandmaples linked to a March of Dimes fundraiser being run by their friend Karen, who recently lost her infant son to a terminal birth defect. She is raising funds to help support research into infant birth defects in memory of her son. You can read more and support their walk here.

[tumblr.com profile] rilee16 is struggling to cover medical expenses after two head injuries last year, and has a fundraiser running to cover living expenses, previous medical bills, and a recent rent increase. You can read more and help out here.

Buy Stuff, Help Out:

Recently I made a post about a new word I'd come up with to describe the gallows humor of Millennials, "Millennihilist", and [tumblr.com profile] dr-kara asked if she could make it into a shirt; the result is on sale now, with all proceeds going to the Hispanic Federation to help with the crisis in Puerto Rico. You can read more, reblog, and find links to purchase here.

Housing:

[personal profile] in_the_bottle is still looking for a roommate; they're looking to let a bedroom just off Fulham Palace Road in Fulham for a short-term from October to 19th November for £850 per month including utilities, negotiable (length of stay also negotiable). You can read more and get in touch here.


And this has been Radio Free Monday! Thank you for your time. You can post items for my attention at the Radio Free Monday submissions form. If you're not sure how to proceed, here is a little more about what I do and how you can help (or ask for help!). If you're new to fundraising, you may want to check out my guide to fundraising here.
[syndicated profile] yuletide_feed

Posted by morbane

In the last four weeks, there have been six works added to the New Year's Resolutions collection. Enjoy!

Friendship (And Beyond) (1313 words) by SegaBarrett
Chapters: 1/1
Fandom: Chess - Rice/Ulvaeus/Andersson
Rating: Mature
Warnings: No Archive Warnings Apply
Relationships: Frederick Trumper/Florence Vassy
Characters: Florence Vassy, Frederick Trumper
Additional Tags: Future Fic, Ex Sex, Getting Back Together
Summary: Florence runs into a familiar face, several years later.


Rubicon (1417 words) by hellabaloo
Chapters: 1/1
Fandom: The Bourne Supremacy (2004)
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Relationships: Jason Bourne/Marie Kreutz
Characters: Jason Bourne, Marie Helena Kreutz
Additional Tags: Grief/Mourning, survivor's guilt
Summary: It was amazingly easy, Jason thought as he watched the pictures burn, to erase any evidence of their two years together.


Whatever Is Has Already Been (1284 words) by snowynight
Chapters: 1/1
Fandom: #FindTheGirlsOnTheNegatives - Anonymous
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Relationships: Woman in Blue Dress/Woman in Red Dress (#FindTheGirlsOnTheNegatives)
Characters: Woman in Red Dress (#FindTheGirlsOnTheNegatives), Woman in Blue Dress (#FindTheGirlsOnTheNegatives)
Additional Tags: Epistolary, Metafiction, Established Relationship, Humor, Unconventional Format
Summary: Barefoot on the Beach (1960) is an underrated gem of a film which still inspires enthusiastic discussion on internet forums, and its promotion still has fostered an internet phenomena #FindTheGirlsOnTheNegatives on Twitter. However, to Helena, the most important influence of the film is to bring her together with Iris.


My Lady Fair Was She (2872 words) by prodigy
Chapters: 1/1
Fandom: Fate/Zero, Fate/stay night & Related Fandoms
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Relationships: Irisviel von Einzbern/Arturia Pendragon | Irisviel von Einzbern/Saber
Characters: Illyasviel von Einzbern, Arturia Pendragon | Saber
Additional Tags: Alternate Universe - Canon Divergence, Berserker Arturia
Summary: Thou, bound in the cage of madness. I am she who commands those chains.


Benjamin's Best (1221 words) by ozsaur
Chapters: 1/1
Fandom: Zootopia (2016)
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Relationships: Benjamin Clawhauser/Original Male Character(s)
Characters: Benjamin Clawhauser, OMC
Additional Tags: benjamin clawhauser - Freeform, Fluff, Pre-Slash, Donuts, Cute
Summary: Surprises are in store for Benjamin.


a word of advice (2967 words) by Himmelreich
Chapters: 1/1
Fandom: Constantine (2005)
Rating: General Audiences
Warnings: No Archive Warnings Apply
Relationships: John Constantine/Angela Dodson
Characters: John Constantine, Angela Dodson
Summary: Angela comes to see John for advice one unpleasantly hot L.A. summer's day.


Until assignments are sent out (approximately) for Yuletide 2017, the New Year's Resolution collection (2017 edition) is open for writers to submit fics based on prompts from previous Yuletides.

Writers are especially encouraged to write stories for prompts that were not filled during the main Yuletide run.

2016 prompts on AO3
Google spreadsheet of all prompts (thank you to Min)
Database of 2016's Dear Author letters (thank you to lsellersfic)
2016 prompts as a text file
Prompts from 2016's non-signed-up pinch hitters on LJ and on DW
Some Day My Fic Will Come mini-challenge - This challenge is for prompts that are posted year after year after year - see more info at the link!


Fics written for the purpose of re-qualifying for Yuletide must be posted before signing up to Yuletide 2017 (ie, before October 9 and ideally before October 1). You have two weeks! They must also be over 1,000 words and written to a previous Yuletide prompt. The fandom in which they are written must still be small enough to qualify for Yuletide (in brief: there are fewer than 1,000 fics each (that are over 1,000 words, in English, and complete) when adding the total fics on AO3 and ff.net).


Recent posts of interest:
Praise Your Fandoms post on LJ | on DW
Misses Clause Challenge on LJ | on DW
Writing Meetups Post on DW
copperbadge: (Default)
[personal profile] copperbadge
R: [chess partner] lost one of my black bishops from the chess set last weekend.

Sam: You should go to the thrift store and find something cool to replace it with! That’s how you get a really unique chess set.

R: So you’re saying his mistake became….a mistakapportunity? 

Sam: Of the millions of words that I thought you might say when you paused, mistakapportunity didn’t even make the list.

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via IFTTT

Ow. My heart.

Sep. 24th, 2017 06:50 pm
[syndicated profile] thebloggess_feed

Posted by thebloggess

Today is Hailey’s birthday.  She’s now officially a teenager, which seems wrong because this was her yesterday: Or maybe it was seven years ago. Feels like yesterday. Except yesterday she was still a pre-teen and two days ago I tucked … Continue reading
[syndicated profile] ted_video_feed
With more than half of the world population living in cities, one thing is undeniable: we are an urban species. Part game, part urban planning sketching tool, "Cities: Skylines" encourages people to use their creativity and self-expression to rethink the cities of tomorrow. Designer Karoliina Korppoo takes us on a tour through some extraordinary places users have created, from futuristic fantasy cities to remarkably realistic landscapes. What does your dream city look like?

0.5 seconds in the Sun

Sep. 17th, 2017 08:24 pm
[syndicated profile] badastronomy_feed

Posted by Phil Plait

It’s funny — in astronomy, you wouldn’t think split-second timing would be all that critical for getting a good shot of some cosmic object. After all, the galaxies, stars, planets, and more have been around for billions of years. What’s the hurry?

But then, you have to remember that not everything is just sitting out there waiting for the shutter to snap. Some things are moving pretty rapidly, and if they’re close enough to us then the difference between getting a nice shot and a fantastic one can take less than a second.

Here, I can show you. Check this out!

ISS transiting the Sun between two huge sunspot groups. Credit: Dani Caxete

ISS transits the Sun between two huge sunspot groups. Credit: Dani Caxete

That is the Sun (duh), taken by Spanish astrophotographer Dani Caxete. He took this on September 5, 2017. At the time, those two big sunspots groups were visible (called Active Regions 12673 and 12674, the former of which flared several times just days later) — in fact, they were big enough to be spotted with no optical aid; I saw them myself using my eclipse glasses left over from August.

But that’s not all that’s in the shot. Look again: Between the active regions is a decidedly more artificial spot:

Close-up of the ISS transiting the Sun between two huge sunspot groups. Credit: Dani Caxete

Close-up of the ISS transiting the Sun between two huge sunspot groups. Credit: Dani Caxete

 

Yup, Caxete caught the International Space Station as it transited the Sun! The ISS is orbiting the Earth at about 8 kilometers per second at a height above ground of just over 400 km (about 500 km from Caxete, who was in Madrid when he took the shot due to his angle). At that speed and distance, it takes very roughly a half a second to cross the face of the Sun.

To capture it, you can’t rely on tripping the shutter at the right time; it’s better to take video, and then select the frames that show the ISS. This image shows one such frame. Caxete made a nice little video showing his travel across the city, the equipment-setting-up, and then getting the shot:

 

Coooool. I like his ‘scope, too; it’s a Long Perng 80 mm f/6.8 refractor with a Lunt Solar Systems Herschel wedge (which filters the sunlight down to acceptable levels), and a Nikon D610 camera. There’s no substitute for good optics!

As Dani told me, he has something of “an obsession with the ISS.” He took this shot as well:

ISS transits the Moon

ISS transits the Moon. Credit: Dani Caxete

 

Nice. And he has lots of other such images he’s taken (including one I featured on the blog back in 2011, though the ISS had a visitor that day), and I suggest you scroll through them, because they’re very pretty.

Getting a shot like this takes some planning, too. The sky is big, and you have to be at the right spot at the right time to catch the ISS moving across a target like the Sun or Moon. Happily, software packages like CalSky (which is what Caxete uses) make that a lot easier; you give it a location and it can calculate what’s visible in the sky and where, including the Sun, Moon, planets, asteroids, and satellites (including potential transits near your location). It’s not too hard to use and fun to play with, so give it a try.

Not that getting a shot like this is easy. But with all this lovely tech we have handy, it’s a lot easier than it used to be. Still, it takes a lot of experience and perseverance … and a deep love of the chase. I don’t mind a chase myself, given the right circumstances (I traveled to Wyoming for the eclipse last month, after all), but in this case, I’m just glad experts like Caxete and others are willing to drop everything, even for just a short while, to provide the rest of us with such lovely images.

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[syndicated profile] ted_video_feed
In an unmissable talk about race and politics in America, Theo E.J. Wilson tells the story of becoming Lucius25, white supremacist lurker, and the unexpected compassion and surprising perspective he found from engaging with people he disagrees with. He encourages us to let go of fear, embrace curiosity and have courageous conversations with people who think differently from us. "Conversations stop violence, conversations start countries and build bridges," he says.

Surviving September

Sep. 21st, 2017 05:07 pm
[syndicated profile] thebloggess_feed

Posted by thebloggess

There’s something about September that wants to eat you. I wrote that years ago and it’s still just as true today.  In fact, every September for years and years I’ve written a post about how – for me at least … Continue reading
[syndicated profile] badastronomy_feed

Posted by Phil Plait

On the morning of Friday, September 22, 2017, the Earth will experience a close encounter with a spaceborne object. But never fear! We’re perfectly safe. That’s because the space traveler is the NASA probe OSIRIS-REx, and it will pass more than 17,000 km above the Earth’s surface.

The flyby is designed so that the spacecraft will steal a little bit of the Earth’s orbital energy, using it to fling itself up, changing its own orbital plane to match that of its target, the asteroid Bennu. OSIRIS-REx will pass closest over Earth’s south pole, and the Earth’s gravity will naturally bend the probe’s path up, up, and away.

This is the third event in the mission’s life in space, counting launch as the first. It launched a bit over a year ago and was placed into an orbit similar to that of Earth around the Sun. In January 2017 it performed a “deep space maneuver,” firing its engine enough to change its velocity by about 1600 kilometers per hour, putting it on the correct course for the flyby.

If you want the details of this flyby, then (as always) you should check in with my friend Emily Lakdawalla at The Planetary Society, who has the info.

The spacecraft has already been spotted by Earthbound telescopes; the Large Binocular Telescope in Arizona saw it on September 2:

Animation showing the movement of OSIRIS-REx on September 2, 2017, when it was still 12 million km away. Credit: Large Binocular Telescope Observatory

Animation showing the movement of OSIRIS-REx on September 2, 2017, when it was still 12 million km away. Credit: Large Binocular Telescope Observatory

I know, it doesn’t look like much, but c’mon: It was 12 million kilometers away and at a magnitude of 25. The faintest star you can see with your naked eye is 40 million times brighter! So this is actually pretty good.

If I’ve done the math right, it’ll be roughly magnitude 11 or so when it passes Earth on Friday. That’s still faint, though within reach of a good telescope. The mission web page has advice and links for trying to see it. Given how far south it’ll be, that means it’s easiest from southern locations; in Australia the Desert Fireball Network will use the flyby to test out their cameras. They’ll observe OSIRIS-REx from different locations and use that to get its 3D trajectory in space. They use the same technique to track material like meteors burning up in Earth’s atmosphere.

I mentioned three events in the mission’s space life so far, but the fourth event is the big one: arrival. Approach starts in August 2018, when OSIRIS-REx is about 2 million km from Bennu. It’ll begin a series of engine burns to slow its approach relative to the asteroid until it goes into orbit. Starting on October it’ll begin surveying Bennu, and will continue to do so for a year.

The orbit of Bennu (blue) is similar to Earth's. This shows their relative positions on the day of the OSIRIS-REx flyby. Credit: NASA / JPL

The orbit of Bennu (blue) is similar to Earth's. This shows their relative positions on the day of the OSIRIS-REx flyby. Credit: NASA / JPL

Bennu is a pretty interesting asteroid (if it weren’t, then duh, we wouldn’t be sending a spacecraft to it). It was discovered only in 1991, and is on an orbit similar to Earth’s, though slightly bigger, more elliptical, and tilted to ours by about 6°. That’s a substantial inclination, taking a lot of energy to match, which is why the spacecraft is using Earth to whip it around. Bennu only approaches Earth about once every six years (its orbital period is about 1.2 years, so it takes a while for it and the Earth to sync up).

Bennu itself is about 500 meters across, a decent-sized chunk of rock (though it will be the smallest object NASA will have ever had a spacecraft orbit, an interesting statistic). It’s what’s called a B-type asteroid, meaning it’s rich in carbon as well as what are called volatiles: materials with low boiling points. Even though it’s small, it may have water inside it, trapped in materials like clays.

It’s shaped roughly like a top or a walnut, slightly wider than it is high. It rotates once every 4 hours or so. Its overall shape was determined from both radar mapping as well as how it changes brightness with time (for example, a very long object can get much brighter when it’s broadside to you, and fainter when it’s end-on). Interestingly, its mass is low; given its size it’s barely denser than water! It’s likely to be a rubble pile, a collection of loosely bound rocks held together by gravity and other forces. That can happen as an asteroid suffers low-speed impacts over billions of years, shattering it in place. Lots of voids form between the rubble, accounting for the low density.

Other than that, it’s thought that Bennu hasn’t undergone much change since it formed 4.5 billion years ago. It’s hoped to be a time capsule dating back to the formation of the solar system itself!

NASA made this spiffy short video explaining more about Bennu, OSIRIS-REx, and the mission itself:

Oh, one more thing for now: OSIRIS-REx is loaded with instruments to examine the asteroid, including cameras, LIDAR, and a spectrometer. But it also has another package: a sample return capsule (SRC). While at Bennu, it will collect a sample of surface material, squirrel it away inside the capsule, then send it back to Earth! This has been done by a mission before (the Stardust mission to a comet), so it’s tested tech.

Scientists want to collect at least 60 grams of material, though they might get more. The mechanism to collect the sample will puff nitrogen gas onto the asteroid surface and then collect the material that floats off. They have enough gas to try this three times, so it seems likely they’ll get what they need.

Then the SRC will be sent on its way back to our planet, arriving as a fireball in the sky and then falling to Earth in July 2020. It’ll be collected and the samples brought to labs where this pristine asteroid material can be studied in much greater detail than is possible with a spacecraft.

But that’s all still far in the future. First things first! Let’s get the flyby done, and then we can start looking ahead to seeing Bennu up close and personal next year.

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Artwork showing OSIRIS-REx flying past Earth above Antarctica and South America. Credit: NASA Goddard Space Flight Center/University of Arizona
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Posted by Phil Plait

Oh wow, is it time for the end of the world again?

Apparently so. The latest in this incredibly long list of doomsday-prophecies-that-will-never-happen™ is that the Earth will somehow be destroyed on September 23.

This is terrible! Scheduling it on a Saturday keeps it out of the news cycle.

OK, snark aside — and I’ll admit that’s hard after you’ve debunked dozens of these kinds of claims — this particular cry of doomsday seems to be thriving where such things usually do: breathless YouTube videos and Facebook pages that carry a lot of dire warning but very little in the way of actual evidence.

I’m not sure where this one started, specifically; it may be from David Meade, someone who may best be described as a conspiracy theorist. He’s created a horrid combination of Biblical quotes and Nibiru claims (because, of course; more on that in a sec) and predicts the beginning calamity starting on September 23.

The key Bible passage is from Revelation 12:

A great sign appeared in heaven: a woman clothed with the sun, with the moon under her feet and a crown of twelve stars on her head. She was pregnant and cried out in pain as she was about to give birth. Then another sign appeared in heaven: an enormous red dragon with seven heads and ten horns and seven crowns on its heads. Its tail swept a third of the stars out of the sky and flung them to the earth. The dragon stood in front of the woman who was about to give birth, so that it might devour her child the moment he was born. She gave birth to a son, a male child, who “will rule all the nations with an iron scepter.” And her child was snatched up to God and to his throne. The woman fled into the wilderness to a place prepared for her by God, where she might be taken care of for 1,260 days.

[Note: The exact phrasing of this changes depending on what version of the Bible you read; an interesting problem given that, in many cases on the web, the doomsday promulgators are also Bible literalists.]

Right off the bat, let me be clear: The language in many biblical passages, especially Revelation, is vague enough that interpretation is loose, and it’s not too hard to fit lots of different meanings to the words. If you look around hard enough, you’re bound to find something that kinda, sorta, sounds like it works.

In this case, the story goes, the woman in the passage is the constellation Virgo. “Clothed with the Sun” means the Sun is in the constellation, and “the moon under her feet” means the Moon is nearby, too. That part happens all the time; the Sun is in Virgo for about six weeks every year. The Moon is in Virgo for several days during that time, and even “under her feet” (as the constellation is classically depicted her feet are to the east and her head to the west) for a couple of days.

So, why September 23rd of 2017? The key part, as far as I can tell, is the position of Jupiter. The largest planet in the solar system, as seen from Earth, is also in Virgo, and is supposed to represent the child being born — it’s claimed Jupiter leaves Virgo on the 23rd.

Virgo

The constellation Virgo, the Sun, Moon, and various planets shown for September 23, 2017. The claim that she's giving birth to Jupiter myths the spot. Credit: Sky Safari 

 

There are several problems with this. The biggest is also the simplest: Jupiter doesn’t leave the constellation on the 23rd. If you want to be pedantic, the constellation boundaries are well defined officially, and Jupiter doesn’t cross into Libra (the next constellation down the line) until November. If you use the classical astrological boundaries for the zodiac constellations, Jupiter already left Virgo in early September. Either way, Jupiter leaving Virgo on the 23rd doesn’t make sense.

Now, you might say, “Well, Jupiter represents a baby being born, so maybe the 23rd is when Jupiter comes out of the part of Virgo where, y’know, babies are born from.”

That would be a nice try, except Jupiter is nowhere near Virgo’s lady parts. It’s way off to the side, and having had some experience here, I can be pretty sure that’s not where babies come from.

So, Bible aside, what’s the deal with Nibiru?

Well, nothing. I mean, literally. Nibiru doesn’t exist.

artwork of astronaut on Moon watching Earth destroyed

Well, crap. Credit: Dean Reeves, used by permisison

 

According to various conspiracy theorists, though, Nibiru is the name given to a purported giant planet in the outer solar system that sweeps by the Earth every 3600 years causing, well, Biblical disasters (not to be confused with Planet Nine, an as-yet  theoretical planet that could be in the outer solar system). This idea has a long history; it has its roots with the wild claims of Immanuel Velikovsky in the mid 20th century; he figured that Biblical catastrophes described in the Bible were real events, and tried to find astronomical ways to cause them. In the end, his lack of historical scholarship was only outstripped by his lack of astronomical understanding, and he abused astronomy trying to explain imagined historical events (the history of his ideas and how they were treated is fascinating; I dedicated a chapter in my first book, Bad Astronomy, to this).

Still, despite an utter lack of reality, his idea caught on and has been reshaped and reproposed over the years. Zechariah Sitchin used it to dream up a “12th planet” in the solar system, and wrote a series of badly researched books on the idea, and then it was picked up by Nancy Lieder,  who claimed in the 1990s that aliens from Zeta Reticuli were telepathically communicating with her to warn her of the impending destruction of Earth by Nibiru. She predicted very confidently it would come in May 2003.

Despite the lack of an Earth-shattering kaboom on that date, this myth lives on. People who cleave to this idea see evidence of this planet in every photo, every solar storm, everywhere. The fact that scientists (like me) debunk it is only more proof of the conspiracy to hide it from the public. This is what I call a cul-de-sac of logic; once you’re in it, you’ve cut yourself off from any sort of evidence against it. You’re lost.

So, the way Nibiru fits into this weekend’s notpocalypse is that, in the Bible passage, the dragon in the prophecy is Nibiru itself, its immense gravity (which up until now has had precisely zero observable effects on any solar system objects) will drop meteors and comets on us (“Its tail swept a third of the stars out of the sky and flung them to the earth”), and so on.

The thing is, Nibiru is supposed to be a giant planet. Jupiter, the actual biggest planet in the solar system, is easily visible even though it’s hundreds of millions of kilometers away; it’s one of the brightest natural objects in the sky. A bigger planet even closer would be far, far brighter. Yet, when you go outside, nothing like that can be seen.

Huh.

So, this end-of-the-world nonsense is just that: nonsense. It’s the usual stuff from this corner of the ‘net, and I can happily say, “Ho hum.” Nibiru has been the cause of predicted doom and gloom over and over again, and all these predictions have one thing in common: They never happen (remember the Mayan doomsday in 2012?). They can’t happen. As I’ve written many times, if Nibiru were really out there, it would leave an obvious swath of destruction and chaos, altering the planets’ orbits, the asteroids, moons, and everything so profoundly that you could see the effects by simply going outside at night and looking up. Put simply, the solar system as we see it now couldn’t exist in its present form if Nibiru were real.

Therefore, Nibiru isn’t real.

And so, therefore, neither is this next doomsday.

And I’ll admit, this kind of stuff makes me angry. There are people out there who don’t have the experience or astronomical knowledge (or who have mental health issues like anxiety and cosmophobia) to understand just how full of fertilizer so many of these self-proclaimed doomsday prophets are. And these people can get really scared, worrying about a disaster that will never come.

When I look around, I see plenty of very real things to be concerned with. Let’s try to fix the actual world, please, and not worry about ones that are made up out of nothing.

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